Spinal cord stimulation (SCS) has emerged as a viable means of managing chronic pain when conventional therapies, such as pharmaceuticals and surgery, have not been effective. However, the clinical success of SCS has been highly variable and success rates have not improved with time. Conventional clinical SCS, which involves the synchronized delivery of stimulation at a single frequency to all dorsal column fibers originating from the source of pain, both excites and inhibits sensory neurons responsible for relaying nociceptive information to the brain. SCS should inhibit the activity of these neurons to produce a beneficial effect, as sensory neuron activity correlates with perceived pain, but higher frequencies of stimulation, and as a result greater power consumption, are required to overcome neuronal excitation by conventional SCS. Higher frequencies of SCS require more power and may be accompanied by side-effect paresthesias, or tingling sensations associated with neural activation of the dorsal columns and other sensations, that may be intense enough to produce less favorable clinical outcomes.
Asynchronous activation has been proposed as a possible mechanism by which “burst” and “high or kilohertz frequency” SCS exert pain relief without paresthesia, but the parameters used in burst and high frequency SCS are not necessarily optimized for efficacy or efficiency. While some SCS devices may be capable of indirectly producing asynchronous activation of dorsal column fibers through high-frequency (>1.5 kHz) stimulation via multiple electrode contacts, model-based design and direct application of multiple asynchronous (e.g., staggered or random) patterns of SCS at average frequencies in the range of standard frequencies of clinical SCS to produce pain relief have not been explored or previously described.